In this project, we propose to combine mRNA display (a protein design/evolution method) and high efficiency microfluidic sorting to create a new technology-microfluidic mRNA display-for the purpose of enabling design of peptides and proteins that can be used as protein capture reagents. We will develop and apply this powerful new technology toward creating a comprehensive reagent set aimed at the Hepatitis C virus (HCV) proteome. In this section, we begin by describing the existing state-of-the-art in 1) mRNA display-based peptide and protein design, 2) bead-based micromagnetic separations, and 3) give an introduction to the proteins expressed by the HCV that will be the targets of this work. This is followed by our description of how we will integrate these technologies to achieve our goal of high-throughput development of new protein capture reagents.